netdev - Re: [PATCH] rtnetlink: fix data overflow in rtnl

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20201017123411.fs7dktphdhw3boao@lion.mk-sys.cz>
Date:   Sat, 17 Oct 2020 14:34:11 +0200
From:   Michal Kubecek <mkubecek@...e.cz>
To:     zhudi <zhudi21@...wei.com>
Cc:     davem@...emloft.net, kuba@...nel.org, netdev@...r.kernel.org,
        rose.chen@...wei.com
Subject: Re: [PATCH] rtnetlink: fix data overflow in rtnl_calcit()

On Fri, Oct 16, 2020 at 10:02:38AM +0800, zhudi wrote:
> "ip addr show" command execute error when we have a physical
> network card with number of VFs larger than 247.
> 
> The return value of if_nlmsg_size() in rtnl_calcit() will exceed
> range of u16 data type when any network cards has a larger number of
> VFs. rtnl_vfinfo_size() will significant increase needed dump size when
> the value of num_vfs is larger.
> 
> Eventually we get a wrong value of min_ifinfo_dump_size because of overflow
> which decides the memory size needed by netlink dump and netlink_dump()
> will return -EMSGSIZE because of not enough memory was allocated.
> 
> So fix it by promoting  min_dump_alloc data type to u32 to
> avoid data overflow and it's also align with the data type of
> struct netlink_callback{}.min_dump_alloc which is assigned by
> return value of rtnl_calcit()

Unfortunately this is only part of the problem. For a NIC with so many
VFs (not sure if exactly 247 but it's close to that), IFLA_VFINFO_LIST
nested attribute itself would be over 64KB long which is not possible as
attribute size is u16.

So we should rather fail in such case (except when IFLA_VFINFO_LIST
itself fits into 64KB but the whole netlink message would not) and
provide an alternative way to get information about all VFs.

Michal